estimate_audience_size

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are provided, so the description carries the full burden. It declares that the tool returns estimated reach with lower/upper bounds, and the example implies a read-only operation. However, it does not disclose authorization requirements or rate limits, but these are less critical for an estimation tool.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is concise (three sentences plus an Args section), front-loaded with the purpose, and well-organized. Every sentence adds value without redundancy.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the simple tool (2 parameters, no output schema), the description is complete: it explains the purpose, return value, and parameter details. The example for targeting_json enhances clarity. No gaps remain.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The description includes an Args section that adds meaning beyond the schema: account_id is described as 'Ad account ID (e.g., 'act_123456789')' and targeting_json as 'JSON string of targeting spec' with an example. This provides clear guidance on format and usage, compensating for the schema's lack of descriptions.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool's purpose: 'Estimate audience reach for a targeting specification.' It specifies the verb (estimate) and resource (audience size), and the return type (estimated daily reach lower/upper bounds). This distinguishes it from sibling tools like search_interests or get_insights.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies usage (when you need estimated reach for a targeting spec) but does not explicitly state when to use this tool vs alternatives, nor does it provide exclusions or conditions. The usage context is clear enough but lacks explicit guidance.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.